I don't think the Unreal levels are particularly labyrinthine.

They just feel so, when you don't know them and don't know what you're doing or where you're going.

Guess what else feels labyrinthine when you don't know it? Facilities in the real world. School campuses, hospitals, factories, etc.. corridors after corridors, floors, staircases, elevators, wings, hubs, often in a very complex layout.

Once you know the place, it's pretty simple. Once you know the Unreal levels, they really are quite simple.

Games are surrealist works of art, they aren't constrained by such petty concepts as logic and function.